The present invention relates to novel lightweight shoes suitable for horses or any animal requiring hoof protection. Another use of the present invention is to provide lightweight pitching horseshoes for women, children, and the elderly. The foregoing products are prepared from a new class of plastic polymers known as "polyphenylene sulfides" which-when converted into horseshoes for shoeing horses with nails and/or special adhesives or into lightweight sportswear-exhibit a typical metallic sound when struck together or thrown onto solid surfaces, a metallic sound clearly identical to solid metallic horseshoes.
One of the major causes of lameness in hores is the direct result of metal horseshoes. They restrict the natural flexing (i.e. expansion and contraction) of the horse's foot, maximize concussion, cause corns, enhance fatigue from their heavy weight, inflict severe cuts and bruises, and provide inadequate protection. Whether used for pleasure, work, or competition, horses are used on a wide variety of surfaces, natural and/or artificial, which can cause overstressing and can damage tendons, cartilage, and bone. It has been suggested that fatigue failure is a major cause of lameness, and lameness is directly related to the hardness of the surface on which horses are used. A linear, direct relationship between lameness on racetracks and the hardness of the tracks has been demonstrated experimentally. The peak shock-level on a horses's hoof is about 2,000 pounds of force when galloping across pavement or hard dirt and 800-1,000 pounds when on grass. This shock can be greatly reduced by using a shoe that has good shock and impact resistance properties. When shock and concussion are reduced on the horse's feet and legs, lameness is always reduced.
With the increasing number of pleasure horses, work horses (e.g. metropolitan mounted police), and draft horses being used on paved surfaces, there is also concern being given to the damage hard metal shoes cause to the surfaces. Indeed the industry, at large, has expressed growing concern over the above-mentioned problems as well as the subsequent increased costs of street and road maintenance and repair. Horse owners, including trail riders, Amish draft horse users, and municipalities, are anxious to replace hard metal shoes with more resilient, less damaging shoes. Similarly, the destruction and enhanced wear on private barn floors, walkways, and surfaced paths resulting from hard metal horsehoes is significant. Unfortunately, in the past none of the lighter weight plastic shoes have measured up to expectations. Another concern to the horse owner that results from the use of hard metal shoes is the restricted "natural" action of the hoof. When a horse is in motion, the natural movement of the hoof is to expand slightly under weight and to contract when the animal's weight is shifted. Rigid metal shoes restrict this natural hoof action, which further contributes to fatigue and lameness. A further disadvantage to the use of hard, rigid shoes occurs when this natural hoof flexing is restricted by the shoe. This results in a tendency to place considerable stress on the nails holding the rigid shoe to the hoof that normally expands and contracts, causing the loosening of the nails or pulling of the nails through the hoof and eventually throwing the shoe. A heavy, hard metal shoe that comes loose or is thrown can inflict severe cuts or bruises to the animal.
Accordingly, there exists a need for a light-weight, shock absorbent, abrasion resistant, partially-flexible horseshoe that will provide therapeutic advantages to the animal and minimize damage to the surfaces on which the animal is used.
Many attempts have been made in prior art to provide a protective device for the horse's foot incorporating the objectives mentioned above. For example, the hoof coverings described in U.S. Pat. Nos. 4,235,292, and 4,206,811 consist of an integrally-designed steel yoke in a plastic body attached with screws. U.S. Pat. No. 4,346,762 involved a combination of plastic horseshoes wherein two parts were pre-united in the toe region. U.S. Pat. Nos. 4,189,004 3,703,209 and 3,732,929 teach that polyurethane-type horseshoes have desirable characteristics. A hard rubber sheet containing small metal fragments is described in U.S. Pat. No. 3,513,915. Indeed, cast polyurethane horseshoe appear to be the preferred material for flexible horseshoes, as described in U.S. Pat. Nos. 3,494,422, 3,490,536, 3,469,631, and 3,603,402. U.S. Pat. No. 4,496,002 describes the use of polyethylene resin for making horseshoes. The types of shoes as described in these references overcome some, but not all, of the recognized shortcomings of metal horseshoes; none has yet received widespread commerical use.